subcalibre
/ˌsʌbˈkælɪbər/Definitions
1. noun
A smaller calibre than that of a standard weapon, particularly a pistol or revolver with a barrel smaller than its cylinder.
“The subcalibre pistol was used for training purposes due to its reduced recoil.”
2. adjective
Having a smaller calibre than standard.
“The subcalibre rounds were designed for increased accuracy at longer ranges.”